The present invention relates to a power supply circuit and, for example, to a power supply circuit suitable for generating a stable output voltage.
In a semiconductor device, the breakdown voltage of each transistor is lowered with miniaturization of a process. Therefore, a power supply circuit for generating a voltage for driving a semiconductor device is required to generate a stable voltage having a small ripple component (fluctuation range, fluctuation) so that a transistor is not destroyed.
Japanese unexamined Patent Application publication No. 2005-278383 discloses a technique for suppressing a ripple component. The power supply circuit disclosed in Japanese unexamined Patent Application publication No. 2005-278383 includes a charge pump that is driven by a clock signal, a comparator that compares the partial voltage of the output voltage of the charge pump with the reference voltage, and a NAND circuit that controls the availability of a clock signal to the charge pump based on the comparison results of the comparator. Here, in this power supply circuit, the speed of the comparator is controlled so as to be fast from the time when the divided voltage of the output voltage of the charge pump exceeds the reference voltage until the output voltage of the comparator is reversed, and to be slow from the time when the divided voltage of the output voltage of the charge pump falls below the reference voltage until the output voltage of the comparator is reversed. Thus, the power supply circuit can suppress the ripple component of the output voltage of the charge pump when the output current to the load is small.